The present application relates generally to switch mode power supplies, and more specifically to switch mode power converters capable of generating Power-Good signals indicative of whether power corresponding to one or more output voltage channels of the converter is within a predetermined acceptable range.
In recent years, the need for switch mode power supplies or DC-to-DC converters has risen dramatically as Integrated Circuits (ICs) such as Digital Signal Processors (DSPs) and mixed signal ICs have continued to decrease in size while their power consumption has increased. Switch mode power converters are typically employed in such ICs for converting positive or negative input supply voltages to output supply voltage levels that are appropriate for powering circuitry within the IC and/or for powering circuitry externally connected to the IC. For example, a switch mode power converter may be configured for either increasing or decreasing an input supply voltage level provided to an IC.
Conventional switch mode power converters typically generate at least one Power-Good (PGOOD) signal for reporting whether power corresponding to at least one output voltage channel is “good”, i.e., within a predetermined acceptable range. For example, in the event the output voltage level is below a predetermined upper limit (e.g., about 110% of a required output voltage level) and above a predetermined lower limit (e.g., about 90% of the required output voltage level), the PGOOD signal may be asserted high by the converter, indicating that the power provided on the output channel is within the predetermined acceptable range. Further, in the event the output voltage level falls outside the predetermined voltage range, the PGOOD signal may be asserted low by the converter, indicating that the power provided on the output channel is no longer good. It is noted that output current information may be monitored instead of or in addition to the output voltage information, and that the PGOOD signal may be used to report the power condition of the converter based on the output current information. Accordingly, by monitoring the state of one or more PGOOD signals generated by the switch mode power converter, users can readily determine whether output voltage levels and/or output current levels generated by the converter fall within predetermined acceptable ranges.
Although the above-described approach to monitoring output power levels of switch mode power converters has been successfully employed to monitor output power associated with a single channel within a converter, this approach frequently has drawbacks when used to monitor the output power associated with multiple converter channels. For example, to monitor the power associated with more than one channel within a switch mode power converter, a power-good circuit operative as described above may be provided for each converter channel. Further, PGOOD signals indicative of the power condition corresponding to the multiple converter channels may be provided at respective output pins of the converter.
However, using a separate PGOOD circuit for each channel within a switch mode power converter can consume a significant amount of the circuit area available within the converter. For example, a switch mode power converter is typically implemented on an IC chip. Further, because multiple PGOOD circuits employed within the converter may increase the amount of circuit area required on the IC chip, semiconductor die sizes may have to be increased to accommodate the increased circuit area, thereby increasing the overall cost of the converter. Moreover, providing PGOOD signals on multiple outputs of the converter may increase the number of pins on the IC package, further increasing the cost of the converter.
In addition, conventional approaches to monitoring output power levels of switch mode power converters, whether they provide PGOOD signals on single or multiple outputs, have typically required a substantial amount of external logic to implement practical power monitoring schemes, thereby increasing both the complexity and the cost of the converters.
It would therefore be desirable to have an improved method of monitoring output power provided by switch mode power converters that avoids the drawbacks of the above-described conventional output power monitoring techniques.